This movie is totally underestimated. It's worth to watch. One of the best movies I've ever watched. The conclusion of the story can be thougt as a lot of ones. People who underestimated this movie might think that the conclusion is blur. However if my conclusion is right ( there's no right answer in a movie like this though ) I think the story of this movie is logical and great.
ADD:
I just saw some articles and people say that Catharine is the one. If it's the truth,this movie is mediocre.